This invention relates generally to composite magnetic heads and relates particularly to composite magnetic heads operating with respect to a multitrack record carrier.
The requirements for magnetic data storage over the years has resulted in increased requirements for greater and greater data capacities. The search for an increase in data capacity has, of course, resulted in efforts to obtain a greater data density. One means of increasing the density of data stored in a given magnetic data storage medium is to insert a plurality of tracks where a single track was previously utilized or to increase the number of tracks where a plurality of tracks was already utilized. As the number of tracks in a given magnetic data storage medium is increased, often track-to-track spacing, or the distance between data tracks, must be reduced. As the width of the recording track is reduced and the spacing between recording tracks is reduced, the difficulty of aligning the magnetic head with the recorded track increases. Ideally, as the magnetic head is positioned with respect to a given track, it will be aligned exactly with that recorded track. However, due to inherent tolerances and manufacturing techniques an exact alignment of the magnetic head with the recorded track is, of course, not exactly possible. No matter how carefully the magnetic head is aligned to the recorded track, some mis-alignment is always present. This mis-alignment presents noise problems to the magnetic head reading the recorded track because along the edge of the recorded track, which is not exactly aligned, all previously recorded data has not been completely erased. As the magnetic head passes over the recorded track again this previously recorded data along the edge shows up as noise.
Several prior art patents illustrate partial solutions to this problem. U.S. Pat. No. 3,485,958 to Bos et al, Composite Magnetic Recording and/or Playback Head with Two Side Erasing Heads Having Electrically Conductive Strips, provides a general illustration of prior art tunnel erase head formats. In the tunnel erase head format, two narrow erase-only heads are positioned on either side of the main read/write head for the purpose of erasing previously recorded interfering signals which occur as a result of these lateral positioning errors. U.S. Pat. No. 3,562,443 to Bos et al, Composite Recording/Playback Head With Two Trim Erase Heads Oriented at an Angle to the Record/Playback Head, provides another similar example. Similarly, reference may be had to four IBM Technical Disclosure Bulletins which disclose the various means of having side erase magnetic structures. In particular, these are Side Erase Magnetic Head by J. L. Dawson, IBM Technical Disclosure Bulletin Vol. 8, No. 2, July 1965, Page 220; Tunnel Erase Magnetic Transducer by L. G. Hopkins, IBM Technical Disclosure Bulletin, Vol. 8, No. 4, Sept. 1965, Page 603; Integral Transverse Margin Erase Magnetic Recording Head by D. H. McClung, IBM Technical Disclosure Bulletin, Vol. 8, No. 8, Jan. 1966, Page 1044; and Concurrent Write-Tunnel Erase Element Magnetic Transducers by N. J. McWhinney, IBM Technical Disclosure Bulletin, Vol. 9, No. 7, Dec. 1966, Page 775. Reference may also be had to U.S. Pat. No. 3,353,168 to Poumakis, Wide-Record Narrow-Read Magnetic Head, for another general description of another means of controlling the noise due to previously recorded data and a subsequent lateral positioning error.
These documents have addressed the intertrack noise problem due to lateral positioning errors, but they do not address the problem of maintaining record carrier to magnetic head contact, nor do they address the problem of providing support for the record carrier as the magnetic head is laterally aligned with various recorded tracks in the record carrier. With a record carrier which has a plurality of tracks as the magnetic head is moved transversely with respect to the direction of movement of the record carrier, both the contact between the record carrier and the magnetic head and, particularly with respect to magnetic tape, the support for the portion of the record carrier which is not being read or recorded by the magnetic head must be maintained. The prior art references cited do not address this problem at all.
Also, composite magnetic head assemblies of this type, present problems associated with the assembly and testing of the composite magentic head. It is generally costly and inconvenient to completely assemble the entire composite magnetic head, including the coil windings, before testing or maintenance can occur. Furthermore, once the composite magnetic head is completely assembled and then it turns out that the head for some reason is faulty, it is likely that the entire head must be discarded. This is particularly aggrevating with respect to a faulty winding in the coil, for example. If some means were provided whereby the composite magnetic head could be partially disassembled for maintenance and tested in actual use, it is likely that the production yield of such composite magnetic heads could be increased.